added readme

readme.md

+# XRootD Disk Cache Local Access
+
+## Description
+An XRootD - Vagrant setup using multiple XRootD plug-ins to implement fast access for clients to an XRootD Cache sitting on top of a shared filesystem 
+
+##Usage
+-git clone https://git.gsi.de/dc/XRootD-Reps/xrootd-disk-cache-local-access.git --recursive
+-cd alice-xrootd-builder-docker-container/
+-sudo ./start.sh
+-cd ..
+-vagrant up
+-vagrant ssh client
+-./proxyprefixtest.sh 
+
+##Procedure explanation
+###The client wants to copy a file from an external dataserver to the local filesystem:
+-The client employs a plug-in, which prepends the address of the redirector/datamanager.
+-The client then connects to the redirector, which checks for existence of the searched file on the shared filesystem in the used cms-plugin
+	-if the file exists, the client gets redirected to the shared filesystem, where it opens the file locally without involvement of any other server
+	-if the file does not exist, the plug-in redirects the client to the forwardproxy
+		-the client now connects to the forwardproxy, which opens a connection to the externalDataserver
+		-the file gets returned to the client and is simultaneously cached by the proxy on the shared filesystem
+
+##Configuration
+The forwardproxy needs the cache location:
+	-oss.localroot /home/vagrant/shfs
+The manager/redirector needs the cache location:
+	-oss.localroot /home/vagrant/shfs
+The client plugin for the proxy prefix needs the prefix in XrdProxyDefault.conf
+	-proxyPrefix=://192.168.1.200:1094///x
+